AnswersELPGEQ2 MJ Science 3 - 2002100 HCPS v24Magnets and Magnetism

Magnets and Magnetism — Unit test Answers

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1
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Potential difference is measured in which units?

A
volts
B
amps
C
currents
D
watts
2
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Georgia moves an unattached piece of wire back and forth over a magnet. Which best explains what will happen?

A
A current will be induced because the wire moves through a magnetic field.
B
A current will not be induced because the wire moves through a magnetic field.
C
A current will be induced because the wire is not part of a closed circuit.
D
A current will not be induced because the wire is not part of a closed circuit.
3

Which would ultimately cause the armature in an electric motor to spin?

A
The current in the armature stops.
B
The gap in the commutator closes.
C
The current in the armature is reversed.
D
The commutator loses contact with the brushes.
4

Which will a positively charged object attract?

A
an object that has a negative charge
B
an object that has a smaller positive charge
C
an object that has no charge
D
an object that has a larger positive charge
5

What is an advantage of series circuits?

A
Adding more batteries will increase the current.
B
There is more than one path for charges to flow.
C
If one bulb goes out, the other bulbs still shine.
D
Light bulbs get dimmer as more bulbs are added.
6

The diagram shows a coiled wire that carries an electrical current.

Question illustration
A
the magnetic field
B
thermal energy
C
light energy
D
the electric field
7

Tisa makes a diagram to organize her notes about charging objects.

Question illustration
A
Electrons move between objects.
B
The objects do not touch.
C
The objects develop opposite charges.
D
The objects have the same charge.
8

Which device manages the flow of current in an electric circuit?

A
the wire
B
the switch
C
the battery
D
the light bulb
9

A bar magnet is cut in half, as shown. Which shows the pieces after the magnet is cut?

Question illustration
A
2 pieces of broken magnet with a jagged edge on the inside side of each piece. On the left a piece labeled N S from left and on the right a piece labeled N S from left.
B
2 pieces of broken magnet with a jagged edge on the inside side of each piece. On the left a piece labeled N S from left and on the right a piece labeled S N from left.
C
2 pieces of broken magnet with a jagged edge on the inside side of each piece. On the left a piece labeled N and on the right a piece labeled S.
D
2 pieces of broken magnet with a jagged edge on the inside side of each piece. On the left a piece labeled S and on the right a piece labeled N.
10

Which parts of an electric generator are connected?

A
two brushes
B
two slip rings
C
the armature and axle
D
the armature and commutator
11

Ohm’s law describes the relationship between which quantities?

A
voltage, resistance, and ohms
B
resistance, current, and amperes
C
current, voltage, and resistance
D
amperes, ohms, and current
12

Cora, an electrician, wraps a copper wire with a thick plastic coating. What is she most likely trying to do?

A
keep the electric potential of the wire balanced
B
decrease the wire’s resistance
C
increase the voltage produced by the wire
D
keep a current from passing out of the wire
13

An object that is made of which material is likely to be attracted to a magnet?

A
nitrogen
B
nickel
C
paper
D
plastic
14

Aretha measures a circuit at 110 V and 240 . Using Ohm’s law, what can she calculate for the circuit?

Question illustration
A
voltage
B
ohms
C
resistance
D
current
15

How are the current and resistance related when the voltage of a circuit is constant?

A
The current doubles when the resistance doubles because they are directly proportional.
B
The current doubles when the resistance doubles because they are inversely proportional.
C
The current is cut in half when the resistance doubles because they are directly proportional.
D
The current is cut in half when the resistance doubles because they are inversely proportional.
16

Which statement correctly describes Earth’s magnetic field?

A
A compass can lead a hiker to the geographic North Pole.
B
The magnetic pole near the South Pole is a north pole.
C
Compasses point toward a magnetic pole that is a north pole.
D
Field lines circle Earth from east to west.
17

Mateo makes a table of the symbols that represent the parts of an electric circuit.

Question illustration
A
Uses electrical energy
B
Provides electrical energy
C
Measures electric current
D
Controls electric current
18

What causes the poles of the electromagnet in an audio speaker to repeatedly switch directions?

A
a metal striker that pulls on the magnet
B
a diaphragm that vibrates around the magnet
C
a current that rapidly switches direction
D
a device that opens and closes a circuit
19

The image shows the electric field lines around two charged particles.

Question illustration
A
1
B
2
C
3
D
4
20

What is required for an electric charge to flow through a wire?

A
zero resistance in the wire
B
a balance of electric potential
C
high resistance in the wire
D
a difference in electric potential

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